In general, an AC power supply to supply AC power to a device is realized by using a switching mode power supply (SMPS). Noise caused by the switching operation of the SMPS is conducted through an external case provided adjacent to the SMPS, so that the nose is induced into a capacitor included in a noise filter of a power source. In addition, the noise induced into the capacitor of the noise filter is transferred to an input terminal of an AC power source to exert an influence on the operation of other electronic products, which is called electromagnetic interference (EMI). Accordingly, in order to remove the EMI, a line filter is required.
A normal line filter attenuates the noise introduced into a power source line to prevent the malfunction of circuits or components connected to a next terminal or a device connected to an output terminal and reduces conductive noise or radiative noise generated in a switching power source to prevent the EMI from occurring in other external devices.
As typical line filters, there are a line filter employing an EE core or an EI core and a troidal core line filter employing a circular core.
FIG. 1 is a view showing a line filter according to the related art.
FIG. 1 (a) shows a line filter employing an EE core. The line filter employing the EE core has a shape, which may cause leakage inductance at a core bonding section as great current is input thereto and may reduce an inductance value of the whole line filter. Thus, more winding coils are required to maintain the target inductance of the line filter, so the economic efficiency may be degraded.
Meanwhile, FIGS. 1 (a) and (c) show a troidal core line filter employing a circular core. The troidal core line filter may be stably operated, but it is impossible to automatically wind coils around a circular bobbin. Thus, the coil wining work may be manually performed, so that the productivity and the economic efficiency may be degraded.